A positioning method for the main buoy of an acoustic underwater mooring

Abstract

This invention provides a positioning method for the main buoy of an acoustic underwater mooring, relating to the field of acoustic underwater mooring main buoy positioning technology. Specifically, it includes the following steps: using a pressure sensor to measure the pressure at the location of the main buoy, and then calculating the actual depth and settling displacement of the main buoy; indirectly calculating the sound velocity in seawater using a segmented CTD (Cyclic Transmission Device) on the mooring system, and using the sound velocity to calculate the distance between the main buoy and the anchored weight, thereby indirectly calculating the horizontal offset of the main buoy; measuring the seawater current velocity vector in the water area where the main buoy is located using an ADCP (Advanced Directional Phase Array); and installing a current-facing tail fin at the tail of the main buoy to ensure that the main buoy always faces the current, with the opposite direction of the seawater flow being the direction of the main buoy. The technical solution of this invention overcomes the problem of existing technologies being unable to accurately position the main buoy of an acoustic underwater mooring.

Description

Technical Field

[0001] This invention relates to the field of underwater mooring technology, specifically to a positioning method applicable to the main buoy of an acoustic underwater mooring. Background Technology

[0002] Acoustic moorings can be used to detect anomalous acoustic signals in the deep sea, offering advantages such as long monitoring time, high concealment, and immunity to surface weather conditions. With the rapid increase in the number of acoustic moorings deployed, the amount of observational data is also growing exponentially, making data quality crucial.

[0003] The various observation instruments carried by acoustic moorings are mostly mounted on the main buoy, which is then connected to an anchor weight via a cable system. This cable system is typically quite long. When encountering currents, the acoustic moorings tilt under the influence of the currents, resulting in drift, sinking, and lateral swaying. This causes the actual depth of the observation instruments attached to the main buoy to be lower than the preset depth, and the monitoring orientation to shift. These longitudinal shifts and current effects cannot be predicted in advance. If the position of the main buoy cannot be accurately located, some observation instruments may measure depths deeper than the preset depth. For example, if the observation instrument is preset to be attached at a depth of 1000m, due to the drift and sinking of the acoustic moorings and the tilting of the overall cable system, the observation instrument may actually be located at a depth of 1100m. This would lead to the erroneous assignment of a depth of 1100m to a depth of 1000m, resulting in poor data quality. Lateral swaying also affects the determination of the monitoring target's orientation. Therefore, to ensure the normal and effective operation of acoustic moorings underwater, accurate positioning and attitude control of the moorings are crucial. In existing technologies, IMUs (Inertial Measurement Units) can be used to determine rotation angles in real time. However, calculating the rotation angle requires integrating the angular acceleration measured by the IMU. The accuracy of the angle calculation algorithm cannot support long-term underwater use of acoustic buoys. Moreover, high-precision IMUs are not only expensive, but also usually require the integration of satellite or long-baseline positioning systems to correct inertial navigation and improve the accuracy of the calculation. However, underwater satellite systems are not feasible.

[0004] Therefore, a positioning method is needed that can accurately locate the position of the main buoy of an acoustic underwater mooring. Summary of the Invention

[0005] The main objective of this invention is to provide a positioning method suitable for the main buoy of an acoustic underwater mooring, so as to solve the problem that the existing technology cannot accurately position the main buoy of an acoustic underwater mooring.

[0006] To achieve the above objectives, the present invention provides a positioning method suitable for the main buoy of an acoustic underwater mooring, specifically including the following steps:

[0007] S1 uses the pressure sensor to measure the pressure at the location of the main buoy, and then calculates the actual depth and settlement displacement of the main buoy.

[0008] S2 uses CTD sensors arranged in sections on the cable system to indirectly calculate the speed of sound in the seawater, and uses the speed of sound to calculate the distance between the main buoy and the anchored weight, thereby indirectly calculating the horizontal offset of the main buoy.

[0009] S3, the seawater velocity vector in the waters where the main buoy is located is measured using ADCP.

[0010] S4. A tail fin is installed at the tail of the main float to ensure that the main float always faces the current, and the direction of the main float is the opposite of the direction of the seawater flow.

[0011] Furthermore, step S1 specifically includes the following steps:

[0012] S1.1, Install a CTD on the main float. After the main float stabilizes due to settling, use the formula... The pressure value of the main float is measured, where H is the actual depth of the main float measured by the pressure sensor, P is the pressure measured by the CTD, ρ is the density of seawater, g is the acceleration due to gravity, and H1 is the water depth of the sea area where the main float is deployed.

[0013] S1.2, Calculate the settlement Δh:

[0014] Δh = h + H - H1;

[0015] Where h is the length of the main buoy cable.

[0016] Furthermore, step S2 specifically includes the following steps:

[0017] S2.1, using CTD sensors arranged in segments along the cable system, the temperature, salinity, and depth of the seawater are measured to calculate the speed of sound in the seawater:

[0018]

[0019] Among them, v i The speed of sound in seawater; T i Seawater temperature; S i Salinity; Depth: D i .

[0020] S2.2, Calculate the average speed of sound

[0021]

[0022] in, v is the average speed of sound; i and v i-1 Each has a depth of D iand D i-1 Speed ​​of sound at D; 发 D represents the depth of the acoustic wave emitting probe. 收 denoted as the depth of the acoustic wave receiving probe; n represents the number of underwater sound velocity samples.

[0023] S2.3, the acoustic wave transmitting probe and the acoustic wave receiving probe are fixed on the anchor weight and the main buoy, respectively. Calculate the distance x between the main buoy and the anchor weight:

[0024]

[0025] Where Δt is the time difference between the sound wave emitted by the sound wave transmitting probe and the sound wave received by the sound wave receiving probe.

[0026] S2.4, Calculate the tilt angle θ of the main buoy relative to its initial position:

[0027]

[0028] S2.5, Calculate the horizontal offset ΔX of the main buoy:

[0029]

[0030] Furthermore, step S3 specifically includes the following steps:

[0031] S3.1, Calculate the direction angle and tilt angle of ADCP:

[0032]

[0033] Where α is the direction angle of ADCP, β is the tilt angle of ADCP, and h heading p and r represent the yaw angle, bank angle, and roll angle of ADCP, respectively.

[0034] S3.2, using the direction angle and tilt angle of the ADCP, the flow velocity in the ADCP's own coordinate system is converted to the flow velocity in the Earth coordinate system, where u is the east-west flow velocity in the Earth coordinate system, v is the north-south flow velocity in the Earth coordinate system, and w is the vertical flow velocity in the Earth coordinate system.

[0035]

[0036] in:

[0037] R = R(α)·R(β);

[0038] R represents the transformation matrix, R(α) represents the rotation matrix around the Z-axis, and R(β) represents the rotation matrix around the Y-axis; u0, v0, and w0 represent the east-west flow velocity, north-south flow velocity, and vertical flow velocity in their own coordinate system, respectively.

[0039]

[0040] S3.3, calculate the seawater velocity vector V = u + v + w.

[0041] Furthermore, the main float in step S4 includes: an integrally formed ball head, a main body, and a tail. One end of the main body is the ball head, and the other end is the tail. A tail fin is provided above the tail, and the longitudinal extension direction of the tail fin is perpendicular to the horizontal plane. Two balancing tail wings are provided below the tail, and the two balancing tail wings are symmetrically arranged along the transverse central axis of the main float.

[0042] Furthermore, the tail fin facing the current has grooves.

[0043] Furthermore, two balancing tail fins are installed near the tail end face.

[0044] Furthermore, the main body is cylindrical, the spherical head is hemispherical, and the tail is a trapezoidal structure, with the diameter of the tail gradually decreasing from the main body towards the tail end face.

[0045] Furthermore, a side-push motor is installed on the side of the main body.

[0046] Furthermore, a torque measuring instrument is installed below the main body.

[0047] The present invention has the following beneficial effects:

[0048] This invention proposes a spatial positioning and attitude determination method for the main buoy of a deep-sea acoustic mooring system, and corrects the yaw attitude of the main buoy after encountering turbulence, thereby improving the accuracy of the acoustic mooring system in monitoring the azimuth and distance of underwater targets. Furthermore, the sensors used in this invention are primarily those commonly carried on mooring observation systems, making full use of existing observation data within the system, and resulting in low cost. Attached Figure Description

[0049] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0050] Figure 1 A structural diagram of the main buoy body in step S4 of the present invention is shown.

[0051] Figure 2 A schematic diagram of the equilibrium state of the anchorage system under ideal conditions is shown.

[0052] Figure 3 A schematic diagram of the equilibrium state of the anchorage system during offset settlement is shown.

[0053] Figure 4 A diagram showing the positional relationships of the anchorage system is provided.

[0054] Figure 5 The diagram shows the velocity of the main buoy under the impact of ocean currents in a current field with a flow velocity of 0.3 m / s.

[0055] Figure 6 The diagram shows the drag coefficient of the main buoy under a 0.3 m / s current.

[0056] Figure 7 The diagram shows the automatic return of the main buoy to center under the control of the side thrust motor after being subjected to a large torque.

[0057] The reference numerals in the above figures are:

[0058] 10. Ball head; 20. Main body; 30. Tail; 31. Tail end face; 40. Frontal tail fin; 41. Groove; 50. Balance tail fin; 60. Side thrust motor; 70. Torque measuring instrument;

[0059] 1. Main buoy; 2. Cable system; 3. Anchor weight. Detailed Implementation

[0060] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] like Figure 1 The method for locating the main buoy of an acoustic underwater mooring, as shown, specifically includes the following steps:

[0062] S1 uses the pressure sensor to measure the pressure at the location of the main buoy, and then calculates the actual depth and settlement displacement of the main buoy.

[0063] S2 uses CTD (Conductivity, Temperature, Depth) sensors arranged in sections on the cable system to indirectly calculate the speed of sound in the seawater, and uses the speed of sound to calculate the distance between the main buoy and the anchor weight, thereby indirectly calculating the horizontal offset of the main buoy.

[0064] S3, the seawater velocity vector in the waters where the main buoy is located is measured using ADCP.

[0065] S4. A tail fin is installed at the tail of the main float to ensure that the main float always faces the current, and the direction of the main float is the opposite of the direction of the seawater flow.

[0066] This invention proposes a positioning method for the main buoy of an acoustic underwater mooring. When the main buoy is deployed in current-affected waters, the impact of the current, the gravity of the anchor, and buoyancy cause the entire mooring system to dynamically drift. The entire mooring system will inevitably shift horizontally by ΔX in three-dimensional space and experience a certain settlement Δh in the vertical direction. The trajectory of the main buoy caused by the tidal current is roughly an ellipse. Therefore, to achieve accurate positioning, it is necessary not only to determine the displacement of the main buoy's settlement but also its horizontal displacement relative to its initial position and its directional change relative to the initial position. The underwater motion of the main buoy is as follows: Figure 1 and Figure 2 As shown.

[0067] The main float 1 serves as a buoyancy platform, providing positive buoyancy for underwater sensors. It is equipped with various sensors, hydrophones, and acoustic wave receiving probes. Because alarms detected by the hydrophones need to be transmitted in real time, the main float is designed to be horizontal, facilitating the deployment of real-time communication buoys.

[0068] Cable system 2 is made of ultra-high molecular weight polyethylene, featuring ultra-high strength, low elongation, and slight positive buoyancy. It is used to connect the sinker and the main buoy. CTD sensors are arranged in sections on the cable system.

[0069] Anchor weight 3 is connected to main float 1 via cable system 2. Anchor weight 3 has an acoustic wave emitting probe that can emit acoustic signals for acoustic distance measurement.

[0070] Specifically, such as Figure 4 The displacement of the main float's settling is determined by indirect measurement using a pressure sensor. A CTD is installed on the main float. After the float stabilizes due to settling, its pressure value is measured using the formula... The actual depth of the sensor can be obtained. The actual depth plus the mooring cable length minus the water depth of the area gives the vertical settlement Δh.

[0071] Step S1 specifically includes the following steps:

[0072] S1.1, Install a CTD on the main float. After the main float stabilizes due to settling, use the formula... The pressure value of the main float is measured, where H is the actual depth of the main float measured by the pressure sensor, P is the pressure measured by the CTD, ρ is the density of seawater, g is the acceleration due to gravity, and H1 is the water depth of the sea area where the main float is deployed.

[0073] S1.2, Calculate the settlement Δh:

[0074] Δh = h + H - H1;

[0075] Where h is the length of the main buoy cable.

[0076] Specifically, to determine the horizontal distance of the main float's offset, this invention uses the acoustic ranging principle to measure the time difference between the emitted acoustic signal and the received reflected signal to calculate the distance between the main float and the anchored weight. Then, it indirectly calculates the horizontal offset distance ΔX by solving a triangle. The specific operation involves fixing the acoustic transmitting probe and receiving probe to the anchored weight and the main float respectively, recording the initial position of the submersible during deployment; this position is the position of the acoustic transmitting probe. After the transmitting probe emits an acoustic signal, the time difference Δt between the received signal and the emitted signal is calculated, and then... The distance is calculated using a formula. The relative distance x between the two objects can then be obtained using the principle of acoustic ranging.

[0077] When calculating x, underwater sound velocity error becomes the main factor restricting high-precision positioning. Different depths and temperatures all affect the magnitude of underwater sound velocity. If the variation in sound velocity is not considered, the obtained x will have a large error, affecting the positioning of the moored buoy. Therefore, this invention uses a method to reduce sound velocity error suitable for moored buoy positioning and ranging.

[0078] Step S2 specifically includes the following steps:

[0079] S2.1, To improve measurement accuracy, this invention incorporates underwater sound velocity to obtain the average underwater sound velocity. This method can significantly reduce depth measurement errors caused by changes in sound velocity gradients. Using an indirect measurement method, CTD sensors arranged in segments on the cable system are used to measure seawater temperature, salinity, and depth, and the sound velocity in seawater is calculated.

[0080]

[0081] Among them, v i The speed of sound in seawater; T i Seawater temperature; S i Salinity; Depth: D i .

[0082] S2.2, Calculate the average speed of sound

[0083]

[0084] in, v is the average speed of sound; i and v i-1 Each has a depth of D i and D i-1 Speed ​​of sound at D; 发 D represents the depth of the acoustic wave emitting probe. 收 denoted as the depth of the acoustic wave receiving probe; n represents the number of underwater sound velocity samples.

[0085] S2.3, the acoustic wave transmitting probe and the acoustic wave receiving probe are fixed on the anchor weight and the main buoy, respectively. Calculate the distance x between the main buoy and the anchor weight:

[0086]

[0087] Where Δt is the time difference between the sound wave emitted by the sound wave transmitting probe and the sound wave received by the sound wave receiving probe.

[0088] S2.4, Calculate the tilt angle θ of the main buoy relative to its initial position:

[0089]

[0090] S2.5, Calculate the horizontal offset ΔX of the main buoy:

[0091]

[0092] Specifically, for determining the orientation of the main buoy of the underwater glider, this invention uses an ADCP (Advanced Divergence Packetizer) mounted on the glider for indirect measurement. Since the glider and ADCP are aligned in the underwater direction, as long as the main buoy remains in a current-facing orientation, the opposite direction of the current measured by the ADCP is the orientation of the main buoy.

[0093] Because ADCP can measure the frequency shift of scattered signals in stratified water media through acoustic Doppler frequency shift, and obtain ocean current velocity using vector synthesis, the direction of the ocean current can be determined by the vector direction of the three-dimensional flow velocity. In use, ADCP emits acoustic signals into the water, and the particle velocity, i.e., the water current velocity, can be calculated by comparing the frequency of the emitted signal with the frequency of the echo signal reflected by particles in the water. The formula for calculating the relationship between the emitted acoustic frequency and the echo frequency is as follows:

[0094] F d =2F0V / C, V=CF d / 2F0

[0095] Where F d It is the acoustic Doppler frequency shift; F0 is the frequency of the emitted wave; V is the velocity of the suspended material along the direction of the sound beam (flow velocity m / s); C is the speed of sound in water.

[0096] The ADCP used in this invention integrates four transducers, and the axes of all transducers can represent the coordinates of a sound beam. By measuring the velocity components in different beam directions, the ADCP allows any three transducer axes to form a set of independent spatial beam coordinate systems.

[0097] ADCP first measures the velocity components along each beam direction. Then, using the transformation relationship between beam coordinates and its own coordinate system (XYZ, a local coordinate system, with the Z direction aligned with the ADCP axis), it converts the velocity in the beam coordinate system into three-dimensional velocities u0, v0, w0 in its own coordinate system, representing the east-west, north-south, and vertical velocities, respectively. Next, using the direction data provided by the compass and the pitch and roll data provided by the inclinometer, it converts the velocity in its own coordinate system into velocities u, v, w in the Earth coordinate system. The conversion formula involves matrix calculations and also requires obtaining the ADCP's direction and tilt angles.

[0098] Step S3 specifically includes the following steps:

[0099] S3.1, Calculate the direction angle and tilt angle of ADCP:

[0100]

[0101] Where α is the direction angle of ADCP in the horizontal direction, β is the tilt angle of ADCP, and h heading p and r represent the yaw angle, bank angle, and roll angle of ADCP, respectively.

[0102] S3.2, using the direction angle and tilt angle of the ADCP, the flow velocity in the ADCP's own coordinate system is converted to the flow velocity in the Earth coordinate system, where u is the east-west flow velocity in the Earth coordinate system, v is the north-south flow velocity in the Earth coordinate system, and w is the vertical flow velocity in the Earth coordinate system.

[0103]

[0104] in:

[0105] R = R(α)·R(β);

[0106] R represents the transformation matrix, R(α) represents the rotation matrix around the Z-axis, and R(β) represents the rotation matrix around the Y-axis; u0, v0, and w0 represent the east-west flow velocity, north-south flow velocity, and vertical flow velocity in their own coordinate system, respectively.

[0107]

[0108] S3.3, calculate the seawater velocity vector V = u + v + w.

[0109] Specifically, since the method for determining the orientation of the main float requires the main float to always be facing the current, this invention optimizes and improves the structure of the main float to ensure it is always in a current-facing posture, and the effectiveness of this structure has been verified through simulation. Furthermore, a main float yaw attitude correction system is designed to address potential underwater turbulence impacts. This system includes a yaw attitude sensing device, a yaw attitude information processing device, and a yaw attitude adjustment device, used to correct the yaw attitude of the main float. The specific structure of the main float is as follows: Figure 1 As shown.

[0110] The main float in step S4 includes: an integrally formed ball head 10, a main body 20, and a tail 30. One end of the main body 20 is the ball head 10, and the other end is the tail 30. A current-facing tail fin 40 is installed above the tail 30, with its longitudinal extension direction perpendicular to the horizontal plane. Two balancing tail wings 50 are installed below the tail 30, symmetrically arranged along the transverse central axis of the main float. The ball head reduces flow resistance. The two balancing tail wings maintain balance and resist roll. The current-facing tail fin positions the main float in a current-facing posture, improving its ability to resist water flow impact. The main float shell material is made of rust-resistant aluminum alloy 5A06, which has good corrosion resistance and mature processing technology. The main float shell shape is designed based on hydrodynamic theory, featuring a low-resistance, slender teardrop shape with fins and a horizontal single-point mooring method. The main float is equipped with an acoustic vector hydrophone, depth sensor, underwater winch module, connecting cable assembly, data acquisition and processing module, power supply module, and integrated control center. Ensure the center of gravity is below the center of buoyancy. The mooring line is attached to a special lug below the main buoy to ensure the main buoy's horizontal attitude in the ocean current.

[0111] Specifically, the upstream tail fin 40 has a slot 41. The slot can effectively reduce the tendency of the float to tilt under turbulent current interference and maintain its balance and stability.

[0112] Specifically, two balancing tail fins 50 are provided near the tail end face 31.

[0113] Specifically, the main body 20 is cylindrical, the ball head 10 is hemispherical, and the tail 30 is a trapezoidal platform structure, with the diameter of the tail 30 gradually decreasing from the main body 20 towards the tail end face 31. The trapezoidal platform structure of the tail can better guide the water flow smoothly, effectively reduce the generation of wake vortices, and improve the stability of the float.

[0114] Specifically, a side thrust motor 60 is installed on the side of the main body 20. The side thrust motor is a yaw attitude adjustment device and serves as the core component for correcting the yaw attitude of the float. When it receives a signal from the torque sensor, the side thrust motor can respond quickly and actively apply thrust as needed to counteract the torque of the main float, causing it to quickly return to the predetermined attitude and ensuring the stability of the main float of the mooring.

[0115] Specifically, a torque measuring instrument 70 is installed below the main body 20. The torque measuring instrument is a main buoy yaw attitude sensing device, which can monitor and measure the torque changes on the cable caused by the rotation of the main buoy due to the current in real time. When a large torque is detected, the information is immediately transmitted to the control system.

[0116] Next, simulations were used to verify that the improved main floating structure was in a current-facing posture in the ocean basin.

[0117] A deep-sea environment was simulated using ANSYS Fluent, and a current field with a flow velocity of 0.3 m / s was designed. The main floating structure was placed in this current field for simulation experiments, and the attitude changes of the main floating body in the current field were observed.

[0118] like Figure 5 As shown in the simulation experiment, it can be observed that after the main float is placed in the sea area, it actively faces the direction of the ocean current, actively engaging with the current. Within the ocean current area, velocity concentration occurs at the front end of the main float. This is because the pressure exerted by the ocean current on the main structure is relatively high, and engaging with the current causes the front area to bear greater stress. The spherical head design reduces the impact force of the fluid at the front end, resulting in a more uniform stress distribution on the main float structure. As the streamlined main float structure gradually extends, the velocity concentration disappears, while the design of the tail fin guides the water flow to converge at the tail, optimizing the current flow pattern and reducing the probability of current separation. Verification shows that the main float structure provided by this invention can effectively engage with the current and reduce the impact of water flow, improve the fluidity of the main float, and reduce stress concentration problems.

[0119] like Figure 6 As shown, the simulation generated a diagram of the main float's current resistance coefficient. For a conventional spherical main float, its resistance coefficient c in seawater is approximately 0.47, while the current resistance coefficient of this main float, as shown in the simulation, is only about 0.372, which can better reduce ocean current resistance and allow the main float to face the current.

[0120] When the buoy is deflected and rotated due to the impact of turbulent currents, the torque on the main buoy is approximately obtained by collecting the torque of the cable system connected to the main buoy. The stress on the main buoy is then obtained, and the thrust is actively applied by the side thrust motor designed on the side of the main buoy to correct the yaw attitude of the main buoy.

[0121] Assuming the mooring cable at the connection point is approximately rigid and capable of transmitting torque, a torque measuring instrument is installed at the connection point to measure the torque acting on the cable. This torque is then applied to the main buoy, and the impact force acting on the main buoy is calculated as follows:

[0122]

[0123] In the formula, F is the force of the ocean current, T is the torque measured by the torque meter, and r is the horizontal distance from the side thrust motor to the torque meter.

[0124] When the torque measured by the torque meter is low, the side thrust motors do not operate, and the optimized main float structure performs self-correction. When the torque meter detects a large torque, it transmits a signal to the yaw attitude information processing device within the main float. After calculating the impact force on the main float, it transmits a signal to the side thrust motors, which then actively apply a thrust of -F. Subsequently, through the interaction of the side thrust motors on both sides of the main float, the turbulent impact force is gradually counteracted, achieving yaw attitude correction. Simulations show that when the main float encounters turbulence, and the torque measured by the torque meter is approximately 160 N·m, the torque curve after correction by the side thrust motors is as follows: Figure 7 As shown.

[0125] from Figure 7 As can be seen, the side thrust motor can counteract the large torque experienced by the main float. The yaw attitude correction system proposed in this invention has a certain effect, improving the main float's ability to resist turbulence.

[0126] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method of positioning suitable for an acoustic mooring buoy, characterized in that, Specifically comprising the following steps: S1, using the pressure measured by the pressure sensor at the location of the main float, and then calculating the actual depth and settlement displacement of the main float; S2, using the CTD sensor arranged on the cable to indirectly calculate the sound speed in seawater, and using the sound speed to calculate the distance between the main float and the anchor weight, thereby indirectly calculating the horizontal displacement of the main float; S3, using the ADCP to measure the seawater flow velocity vector of the water area where the main float is located; S4, a flow-encountering tail fin is arranged at the tail of the main float, so that the main float always encounters the flow, and the direction opposite to the seawater flow direction is the direction of the main float; the main float comprises an integrally formed ball head, a main body and a tail, one end of the main body is the ball head, the other end is the tail, and a side thrust motor is arranged on the side surface of the main body; Step S2 specifically comprises the following steps: S2.1, measuring the temperature, salinity and depth of seawater by the CTD sensor arranged on the cable, and calculating the sound speed in seawater: ； wherein, is the speed of sound in seawater; is the seawater temperature; is the salinity; and the depth is ; S2.2, calculate average sound speed : ； wherein, is the average sound speed; and are the sound speeds at depths and respectively; is the sound wave transmitting probe depth; is the sound wave receiving probe depth; is the number of underwater sound speed samples; S2.3, the acoustic wave transmitting probe and the acoustic wave receiving probe are fixed on the anchor weight and the main float respectively, and the distance between the main float and the anchor weight is calculated : ； wherein, a time difference between the emission of the sound wave by the sound wave emission probe and the reception of the sound wave by the sound wave reception probe; S2.4, calculate the inclination of the main float relative to the initial position : ； ； wherein, L is the length of the mooring line, S is the settlement; S2.5, calculating the offset of the main float in the horizontal direction : ； Step S3 comprises the following steps: S3.1, calculating the direction angle and inclination angle of the ADCP: ； wherein is the azimuth angle of the ADCP, is the inclination angle of the ADCP, , , respectively represent the yaw, inclination and roll angles of the ADCP.

2. A method of positioning a main float of an acoustic mooring according to claim 1, wherein, Step S1 specifically comprises the following steps: S1.1, install CTD on the main float, after the main float is stable, use the formula Measure the pressure value of the main float, wherein, is the actual depth of the main float measured by the pressure sensor, is the pressure measured by the CTD, is the density of seawater, is the acceleration of gravity, is the water depth of the sea area where the main float is deployed; S1.2, calculate settlement : ； wherein, L is the length of the main float cable.

3. A method of positioning a main float of an acoustic mooring according to claim 1, wherein, Step S3 further comprises the following steps: S3.2, convert the flow velocity in the ADCP own coordinate system to the flow velocity in the earth coordinate system by the direction angle and the inclination angle of the ADCP, is the east-west flow velocity in the earth coordinate system, is the south-north flow velocity in the earth coordinate system, is the vertical flow velocity in the earth coordinate system: ； Wherein: ； representative of a transformation matrix, representative of a rotation matrix around the Z axis, representative of a rotation matrix around the Y axis; , and represent the east-west, north-south and vertical flow velocities, respectively, in the own coordinate system. ； S3.3, calculating the flow velocity vector of the sea water .

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